The present invention relates generally to analog encoders and, more particularly, to a method for initializing an analog encoder to produce desired first and second encoder output signals.
The cost of analog encoders increases as the encoder components such as the encoder mask, light element and photo sensors are made more precise and/or with higher tolerances. When working with less expensive encoders the encoder output signals produced have a tendency to be further removed from ideal signals.
Accordingly, it would be advantageous to provide an encoder to initialization method which adjusts certain control parameters to achieve desired or acceptable encoder output signals.
In one aspect, a method for initializing an analog encoder system which produces first and second encoder output signals from first and second channels is provided. The system including an analog encoder with a light element, first and second photo sensors producing signals as a function of light received, and dc offset circuitry associated with the first and second channels for offsetting the signals produced by the first and second photo sensors. The method includes the steps of: (a) establishing a desired signal range for the first and second encoder output signals, the range defined by a max and a min; (b) repeatedly adjusting an energization level of the encoder light element and a dc offset of each channel to place a max of each channel above an upper threshold which is below the max of the established range and to place the min of each channel below a lower threshold which is greater than the min of the established range; (c) after step (b), adjusting the dc offset of at least one of the channels in order to set a mean of both channels substantially the same.
In another aspect, an initialization method involves: (a) establishing a desired signal range for the first and second encoder output signals, the range defined by a max and a min; (b) setting the encoder light element to a zero energization level; (c) after step (b), adjusting the dc offset of each channel until a maximum amplitude and a minimum amplitude of each channel are within the established range and the maximum amplitude of each channel is near the max of the established range; (d) after step (c), increasing an energization level of the encoder light element in a series of increments until the minimum amplitude of at least one of the first and second channels is below a low threshold; (e) after to step (d), adjusting the dc offset of each channel to move the maximum amplitude of each channel near the max of the established range; (f) after step (e), increasing the energization level of the encoder light element in a series of increments until the minimum amplitude of both of the first and second channels is less than another low threshold.
In a further aspect, an initialization method involves (a) establishing a desired signal range for the first and second encoder output signals, the range defined by a max and a min; (b) setting the encoder light element to a zero energization level; (c) adjusting the dc offset of each channel until a maximum amplitude and minimum amplitude of each channel is within the established range and the minimum amplitude of each channel near the min of the established range; (d) after step (c), increasing an energization level of the encoder light element in a series of increments until the maximum amplitude of at least one of the first and second channels is above a high threshold; (e) after step (d), adjusting the dc offset of each channel to move the minimum amplitude of each channel near the min of the established range; (f) after step (e), increasing the energization level of the encoder light source in a series of increments until the maximum amplitude of both of the first and second channels is above another high threshold.